Saturday 19 May 2012 17.54 EDT
First published on Saturday 19 May 2012 17.54 EDT

Ed Miliband is being urged by a growing number of shadow cabinet members and senior allies to promise a dramatic in-out referendum on Britain's future membership of the European Union if Labour wins the next general election.

Several figures in the party are pushing the Labour leader to make the pledge well before the next European elections in 2014 to outmanoeuvre David Cameron, who is under heavy pressure to commit the Tory party to a national vote on the issue. The Observer has been told that, after discussions with shadow cabinet members, Miliband is leaving the door open to a referendum – although he is keen to stress that the short-term focus and discussion must be on how to end the current euro crisis.

Allies of the Labour leader say pressure on him to make what would be a historic, high-risk pledge will increase following the appointment of Jon Cruddas, the MP for Dagenham and Rainham, as Labour's policy chief.

Cruddas, a long-time opponent of the euro but otherwise pro-EU, is strongly in favour of an in-out referendum as a means of ending divisive arguments on Europe once and for all. Before his appointment, Cruddas told the People's Pledge campaign for a referendum that the issue was one of "democracy", and said a referendum pledge should be made "immediately, or as quickly as we can". Cruddas is understood to think that such a move would help define Miliband's leadership as bold and distinct from the New Labour years of Tony Blair and Gordon Brown.

A ComRes opinion poll for the Independent on Sunday and Sunday Mirror showed how Europe is emerging as an issue that could be pivotal at the next election. The poll showed that 26% of Tories now say they will consider voting for the anti-EU Ukip compared to 11% of Labour supporters and 14% of Liberal Democrats. It also showed the extent of anti-EU hostility Labour would need to overcome if a referendum were held now, with 46% of voters saying they would vote to leave the EU compared with 30% who would vote to stay in.

If Labour did commit to a referendum, the party leadership would campaign vigorously in favour of a vote to stay in – a stance that would be supported by most Labour members.

A referendum would, however, leave the Tories divided, with the party leadership certain to campaign for a vote to remain in the EU, while many MPs and grassroots Conservatives would want to leave. One shadow cabinet member said: "We should have the confidence to say we think we can win this and get on with it. There are issues of timing, about when we make the decision and when one would be held. But it certainly is no longer heresy to talk about it."

A spokesman for Miliband did not deny that the option was being considered, stressing merely that "our position is that we don't think this is what Europe needs at the moment".

Last week, in a sign that the Labour party is gradually preparing the ground for a referendum pledge, shadow chancellor Ed Balls said there could be a case in future, for calling a national vote when the current euro crisis was over and the shape of the new Europe was known. This followed similar comments from former cabinet minister and European commissioner Lord Mandelson.

On Thursday Peter Hain, a former Europe minister who stepped down from the shadow cabinet last week but who remains loyal to Miliband, said on BBC1's Question Time that he believed the British people would deserve a say when the time was right. "I think the way things are going people in Britain probably want to make up their minds about whether to stay in Europe or not," he said. "I don't think we should be frightened about giving people a vote."

Sources said that Hain would never have spoken out on the EU issue had he felt such remarks would have been unhelpful to Miliband, or significantly out of kilter with the Labour leader's own views.

Miliband is said to be genuinely undecided and cautious – not least because of the possibility that the country could vote to leave the EU. He is also being advised by some that the move could be seen as crudely opportunistic at a time of crisis in the EU.

Others say that it could put off Liberal Democrats who might otherwise come over to Labour.

Labour enthusiasts for a referendum stress, however, that it would not in any way amount to a watering down of Labour's commitment to the EU. On the contrary, it would be an opportunity to argue the positive case for membership during a national campaign – one that would also help the party build alliances with pro-EU elements of the business community.

While a minority of Labour MPs might want to leave the EU, highlighting divisions within Labour, they say a referendum would cause far deeper splits in the Tory party.

The People's Pledge, which draws support from all political parties, has announced it will hold more local referendums in three Greater Manchester constituencies, Withington, Cheadle and Hazel Grove, asking people if they want a national vote.

The seats, one in Manchester and two in Stockport, are all represented by Liberal Democrat MPs: John Leech, Mark Hunter and Andrew Stunnell, respectively. This follows its local referendum in Thurrock last month where 89.9% of people who voted backed a referendum.

Ian McKenzie, director of the People's Pledge, said: "The people of Thurrock set the pace last month by voting in huge numbers for a referendum. Voters in Manchester Withington, Cheadle and Hazel Grove now have the chance to quicken that pace towards a national referendum for the rest of us."